real housewife of Beverly hills star battling Lyme disease. Yolanda foster is revealing she's paying big changes in her lifestyle to focus on getting healthy. Cecilia Vega has her story. Reporter: Glamour made for reality TV. Married to David foster. Hi. Reporter: But behind the doors of her mansion, Yolanda foster has been in a very real fight for her life. A battle against Lyme disease that played out on bravo's show "The real housewives of Beverly hills." Lyme disease has really severely attacked my brain. Reporter: Built all of this. With the reality TV cameras off she invited us in opening up her home. What is all of this? Like all the pills I take. This is one day of, you know, just my vitamins. Reporter: To reveal her struggle. It's such a lonely disease and it's so siement. Reporter: Lyme disease can carried by ticks after a bite it can enter the bloodstream attacking the skin joints and nervous system. Yolanda is not exactly sure how or when she contracted it. It started with memory loss and difficulty focusing. And I couldn't read or write or watch TV or do anything. Reporter: On your worst day, what did it feel like? I'd get emotional just thinking about it. You know. Just -- you know, how am I ever going to get out of this. Reporter: The recovery has been painful from having a port implanted to get antibiotics into her bloodstream quickly to visits with doctors around the world. Now a clinical trial where she says these machines help repair damaged brain pathways. I'm determined and I'm going to beat this thing. Everybody is telling you it's in your head. Reporter: Hardly alone. There are more than 300,000 new cases of Lyme disease every year in the U.S. And even though Yolanda is getting better, she feels she can no longer manage the couple's stunning 12,000-square-foot mansion. Reality TV's perfect pad is just too much work for Yolanda in her new real-life reality with Lyme disease. So she's had to put her dream house on the market for a reported $27.5 million. I really am not that attached to materialistic things. You know, I can make any home house a home. Reporter: For "Good morning America," Cecilia Vega, ABC news, malibu, California. Let's talk about this now with Dr. Jennifer Ashton. I was surprised to see though it could progress this far. Absolutely can and the problem, you guys, is that the symptoms are so vague they overlap with a lot of other -- What about the bull's-eye? That occurs in about 70% or 80% of people who get bitten by this deer tick, a bacterial infection but the remaining 20% to 30% never get that hallmark bull's-eye rash or these vague Simms like fatigue, chill, body ache, fever, headache. I mean -- You think we all -- Exactly and that's the problem is that it can be undetected, misdiagnosed and progress from days to weeks to months to years. How debilitating can this be? It can be incredibly debilitating. This can affect basically every major organ system in the body. Incredible to think so many bad things can come from such a small deer tick but can hit the joint, the heart, the central nervous system and even disturb mood so it's a big problem. What's the prognosis here in this case? It's vaerable, Lara. In some cases if it's treated with simple courses of antibiotics people can recover and do well but it's variable. It's uncertain and people who have had it for years can go into a chronic disease state so even though we see more of it in the months of the summer it is detected every month out of the year. I was just going to say, you know, with Sarina spring comes, we start wrapping them up, you know, you look over them if they're in heavily wooded areas. What else can people do. Look at a map of the country. Again, these deer ticks tend to be concentrated in the northeast in Minnesota in Wisconsin, so if you're going to be traveling to those areas your awareness needs to be up. When you're coming back from inside, inspect your body, inspect your clothes and pets. These deer ticks tend to go to the armpits and groin and shower them off. Thanks very much. All right, thank you.

This transcript has been automatically generated and may not be 100% accurate.

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